<!DOCTYPE html>
<html>
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>
<body>
  <script>
    const fn = v => {
      alert(v);
    };
    fn(20);
  </script>
</body>
</html>